Give it time and horsepower will increase in new locomotives. Just look back in history to the 60's, 2500 hp was the max until the 3600hp SD45 came out. That increased hp ratings available by 1100 hp. far higher increase than at any time before. But in time the hp rating settled down at 3000 hp. then in the 80's it went up the the 4000+ range. So it would show that horsepower will again increase when older 4000-4400 hp engines need replacing and train sizes and weight have increased. I think in time models like the SD80ACe will replace older units like SD70M(AC) and C44-9W's.
Locomotive performance has reached a plateau because we have reached the practical limits for steel on steel factors of adhesion. The theoretical limit is slightly above 50%, the practical limit under good but not perfect conditions is about 43% for a well maintained locomotive. The only locomotives that can achieve these figures are those equipped with 3-phase Asynchronous AC Drive. Unless the railroads want to run faster trains or change to locomotives with 8 powered axles, or go to road slugs, there is no reason to increase horsepower above the current plateau.
CSXT's high-tractive-effort AC4400CWs and ES44ACs, which have nominal weights of 432,000 pounds, can attain adhesion levels of 46%. They could exceed that if they were not limited, because of coupler-strength concerns, to producing 200,000 pounds of tractive effort.
Well, tell that to Europeans routinely putting more than 1.5 MW per axle in their electric locomotives.
Typical power to the rails for a high performance electric locomotive is 6.4 MW (transformer output is around 7.1 MW), for a 4-axle locomotive. For a 6-axle electric locomotive, you can go to a company like Bombardier or Alstom and order 9.6 MW power.
And all that at nearly 21 tonnes/axle.
Cheers,
N.F.
The high power to the motor is great if you are looking for lots of speed. Will that locomotive generate 200,000 lbs of 'continuous' tractive effort? Remember, we are dealing with a self contained power supply in a diesel electric. And as mentioned, 43-50% adhesion is the practical limit right now - adding HP will add little except cost - unless you are looking for super acceleration. This is not the AAR 'Nationals' drag race!
Jim
Modeling BNSF and Milwaukee Road in SW Wisconsin
I am wondering if railroads could get away with 2x 4000/4400 HP AC locomotives and a 6 axle AC slug between them instead of 3 4400 AC locomotives in low speed coal service?
They could use 3x 3000HP AC locomotives, if such a beast were available, but it would be more fuel efficient to use 2 AC locomotives and an AC slug if that would provide sufficient HP when combined with the 18 powered AC axles.
Well, tractive effort is depending on weight on driver wheels (and adhesion factor), not horsepower per se.
If you can, compare tractive effort curves from the same locomotive platform but with different horsepower. You will note that, up to the 'critical speed' (which is weight-limited) the performance is the same, but the curve that falls slowly (and which is horsepower-dependent) is moved to the right.
F=m*a is the whole story after the critical speed.
And 'horsepower talks' if you are not doing a coal drag but you want to have a fluid railroad, since you can keep the same speed with fewer locomotives (you can have two 6000hp locomotives instead of three 4300hp ones). Obviously, European electrics are different beasts, but I would like to see the incoming Amtrak 6.4MW boxes pulling fast freights as an experiment.
For USA locomotives, the practical limit is either a 20-cylinder 710G motor (around 5500hp) or a pair of medium speed diesels like the Caterpillar C175 or the MTU R4000 with automatic start-stop for better fuel economy (you keep only the one diesel for switching or idling).
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The CSX limit is 2 6 axle AC + 1 dash-8 DC for max tonnage unit trains. Max tonnage mixed freight trains is 3 Dash-8's.
TE of 3 AC's exceeds the published knuckle strength of the high tensile knuckles used in unit train service; additionally with the high degree of curvature that is in the CSX mountain routes excessive power on the head end makes stringlining a real possibility.
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For this reason, modern electric locomotives like the Bombardier TRAXX have a 'tractive effort limiter' in software.
If my memory serves me correctly, when working in double-heading, such locomotives limit automagically the coupler effort to 250 kN each (total 500 kN in double heading), in order to avoid breaking the anemic UIC screw couplers in mountain routes (grades up to 2.8% - in Alpine routes, so you need all the horsepower you can get, if you want to keep the railroad fluid).
Of course, after the 'critical speed' you give it all the power you can get.
nfotis For this reason, modern electric locomotives like the Bombardier TRAXX have a 'tractive effort limiter' in software. If my memory serves me correctly, when working in double-heading, such locomotives limit automagically the coupler effort to 250 kN each (total 500 kN in double heading), in order to avoid breaking the anemic UIC screw couplers in mountain routes (grades up to 2.8% - in Alpine routes, so you need all the horsepower you can get, if you want to keep the railroad fluid). Of course, after the 'critical speed' you give it all the power you can get. Cheers, N.F.
Europe isn't handling 6500 foot 20000 Ton trains on 1 & 2 percent grades.
Well, if Europe is not a fair comparison, what about China?
http://en.wikipedia.org/wiki/Daqin_Railway
In this route, they are handling 20.000 metric tonnes coal trains with locomotives like this one:
http://en.wikipedia.org/wiki/China_Railways_HXD1
And you can see these lowly locomotives in action:
http://www.youtube.com/watch?v=AoLxOJM0z9A
And to give an additional data point, the 4-axle Siemens Vectron in their 6.4 MW configuration can pull a 1600 metric tonnes train at up to 120 km/h, or a 550 tonnes passenger train at 200 km/h
(conversion to imperial units is left as an exercise to the reader )
When speaking about diesel locomotives pulling freight trains at rather grades, typically it is preferable to use the smallest possible prime mover for going over the hump, as the fuel consumption is directly proportional to horsepower. The higher speed does not gain enough time for balancing the higher fuel consumption, as I have found from my simulations.
The mechanical dept. folks at CSX would disagree with you about that..they were satisfied enough with the performance of their AC6000CW fleet to rebuild them with newer 16 cylinder GEVO engines with the same HP rating.
So although the North American industry as a whole didn't not find 6,000 HP diesels to be cost effectice there is that significant exception..
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Well, as you noted, this was an exceptional case which involved a locomotive that ceased production in 2001 according to http://en.wikipedia.org/wiki/GE_AC6000CW
European electric locomotives like the TRAXX (the light sister of the ALP-46) or the Vectron (small sister of ACS-64) are in production today, with power to the rails ranging from 5.2 to 6.4 MW
(note that the diesel prime mover ratings lose 15-20% when these apply to the rails, so the difference is even more pronounced).
At any rate, I hope that I made my point about the limits of power per axle: the current state of the art is nearly 2.000/axle.
No matter the Horsepower or Megawatts
Wheel slip control is the name of the game to move freight.
nfotis Well, tractive effort is depending on weight on driver wheels (and adhesion factor), not horsepower per se. If you can, compare tractive effort curves from the same locomotive platform but with different horsepower. You will note that, up to the 'critical speed' (which is weight-limited) the performance is the same, but the curve that falls slowly (and which is horsepower-dependent) is moved to the right. F=m*a is the whole story after the critical speed. And 'horsepower talks' if you are not doing a coal drag but you want to have a fluid railroad, since you can keep the same speed with fewer locomotives (you can have two 6000hp locomotives instead of three 4300hp ones). Obviously, European electrics are different beasts, but I would like to see the incoming Amtrak 6.4MW boxes pulling fast freights as an experiment. For USA locomotives, the practical limit is either a 20-cylinder 710G motor (around 5500hp) or a pair of medium speed diesels like the Caterpillar C175 or the MTU R4000 with automatic start-stop for better fuel economy (you keep only the one diesel for switching or idling). Cheers, N.F.
efftenxrfe Pete1950 directs this correctly. Consider loadmeters show amperage representing one or two moter's draw from the engine/generater. Consider that at starting a train, amperage may get to 1250 (or more). 6-moters at 1250 amps. Horsepower is 740 or-so watts. Watts are volts times amperes. Locomotive generaters max out at about 900 volts, though 600 volts is the advertised rate. So, solve for 6 moters at 1200 amp's using 600 (or so) volts and look at the HP required to produce 1200 amps, based on 740 watts a horsepower. Ed Wheelighan explained this to me in '1981 from EMD to the SP Engine Service Training Center during fuel-saving directives.
Pete1950 directs this correctly. Consider loadmeters show amperage representing one or two moter's draw from the engine/generater. Consider that at starting a train, amperage may get to 1250 (or more).
6-moters at 1250 amps.
Horsepower is 740 or-so watts.
Watts are volts times amperes.
Locomotive generaters max out at about 900 volts, though 600 volts is the advertised rate.
So, solve for 6 moters at 1200 amp's using 600 (or so) volts and look at the HP required to produce 1200 amps, based on 740 watts a horsepower.
Ed Wheelighan explained this to me in '1981 from EMD to the SP Engine Service Training Center during fuel-saving directives.
@beaulieu:
Really, I do not understand this argument about stopping/braking trains.
After all, braking power rises symmetrically with the number of wagons.
I put forth the argument that horsepower is needed if you want a fluid railroad.
With the same number of locomotives you can get higher productivity. Obviously, if you have a single-tracked railway with sidings, this advantage will be lost.
A single track main line with an adequate number of sidings can run 80% of the traffic of a two track main line.
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Any citation please?
The percentage looks extremely high to me for conventional single-track operation, and it could probably attained while 'ganging' groups of trains (three eastbounds in a row, three westbounds after that, etc.)
Note that accelerating/decelerating a heavy freight train for entering/leaving a siding means much less capacity compared to a steady parade of dedicated tracks for each.
To tell the truth, whatever improvements are done on the mainline, if you yards are plugged and without capacity to accept/deliver trains you will be severely limited in throughput.
nfotis @beaulieu: Really, I do not understand this argument about stopping/braking trains. After all, braking power rises symmetrically with the number of wagons. N.F.
Double the cars you double the braking power, double the speed you need to quadruple the braking power. Take a loaded coal train from 40 to 60 mph, the stopping distance will about double. North American freight cars when loaded are about 60% heavier on the same number of axles, compared to European freight wagons. While I believe North America freight have more braking power, they don't have 60% more.
Braking power is fully discussed in this NTSB derailment report
http://www.ntsb.gov/doclib/reports/2002/RAR0202.pdf
Well, first I didn't say you would use these more powerful locomotives for going downgrade
(if I left such an impression, apologies - English is not my native language)
Second, I did not speak about moving heavy trains at 100+ mph. Rather, I suggested e.g. going from 20mph to 40mph upgrade, in order to have more homogeneous train speeds.
You are right in that kinetic energy is related to the square of speed. But then you seem to forget that brake force is not proportional to speed, either. And I have not mentioned ECP brakes. Note that going down a mountain is not so much about managing kinetic energy, but rather you manage gravitational potential energy (= height difference). According to the train handling applied, this potential energy will get converted to heat (via braking), electricity (regenerative rheostatic braking) or kinetic energy.
Also, dynamic (and rheostatic) braking in locomotives becomes more powerful all the time, to the point that it may damage the couplers when being in multiple traction, so you have to limit this.
Of course, even in a slow train you can bleed the air or do repeat brake applications in a way that zeroes the braking capability. Going slowly might give you some time to recharge the air brakes (maybe) while dynamic brakes try to keep the train under control.
The UIC railways have graduated air brakes, which behave differently (you can apply X braking power, then raise it to Y and later return to X without the need to release brakes fully for recharging air - the price for this is slower reaction in very long trains).
Witness the Malmbanan in Sweden, where 8500 metric tonnes iron ore trains go downgrade from Kiruna to Narvik with a single two-section IORE electric locomotive, at some really nasty grades.
Are these being made in Muncie???
cat992c Are these being made in Muncie???
nfotis You are right in that kinetic energy is related to the square of speed. But then you seem to forget that brake force is not proportional to speed, either. And I have not mentioned ECP brakes. Note that going down a mountain is not so much about managing kinetic energy, but rather you manage gravitational potential energy (= height difference). According to the train handling applied, this potential energy will get converted to heat (via braking), electricity (regenerative rheostatic braking) or kinetic energy.
BNSF's System Special Instructions says that trains having a weight of less than 100 Tons per Operative Brakes allowed to operating at a speed of 60 mph, any train having a weight of 100 Tons per Operative Brake or more is limited to a top speed of 45 mph. Of course speeds can also be limited due to Hazmat cars, or curves, or grades, or turnouts, or other speed restrictions.
Here is the restriction for Cajon Pass on the North Track (the easier grade), without helpers
Speed limit if train weight does not exceed 6500 tons and 95 TPOB 30mph
Speed limit if train weight exceeds 6500 tons or 95 TPOB 20mph
Train not permitted to operate if it exceeds 14,000 tons
With helpers
Speed limit if train does not exceed 6500 tons and 135 TPOB 30 mph
Speed limit if train does exceed 6500 tons but less than 12,000 tons and not more than 135 TPOB 25mph
Speed limit if train exceeds 12,000 tons but does not exceed 135 TPOB 20mph
Train must not operate if it exceeds 16,000 tons or exceeds 135 TPOB
Also, dynamic (and rheostatic) braking in locomotives becomes more powerful all the time, to the point that it may damage the couplers when being in multiple traction, so you have to limit this. Of course, even in a slow train you can bleed the air or do repeat brake applications in a way that zeroes the braking capability. Going slowly might give you some time to recharge the air brakes (maybe) while dynamic brakes try to keep the train under control. The UIC railways have graduated air brakes, which behave differently (you can apply X braking power, then Cheers, N.F.
The UIC railways have graduated air brakes, which behave differently (you can apply X braking power, then
Hello,
if I understand correctly, TPOB means tonnes per wagon brake rig?
I mean, you have two bogies, each with its own brakes. You seem to say that these two bogies must carry no more than 100 tonnes (total wagon weight?) if the loaded train is permitted to operate at 60 mph (nearly 100 km/h).
This is reasonable, we in Europe have similar constraints but expressed in metric tonnes/axle usually (typical situation):
- run at 20 tonnes/axle load: 120 km/h (75 mph)
- run at 22.5 tonnes/axle load: 100 km/h (62 mph)
So, a 4-axle wagon could run on a flat or rising route at up to 62 mph loaded at 90 metric tonnes (= 99 tons) total weight. That is practically equivalent between us, don't you think?
The speed limit on down grade does have to do with the combination of grade and kinetic energy, and it must include: track curvature and thermal capacity of air brakes. As per the NTSB report mentioned above, the dynamic braking must not figure in this calculation - the air brakes must be enough for fully stopping the train.
Now, what happens when you have empty wagons in your train? Does their braking force enter the calculation? I suspect that the numbers you quoted above are *average* numbers for the whole consist.
nfotis Hello, if I understand correctly, TPOB means tonnes per wagon brake rig?
Almost, once in a while a train will have to move a car with inoperative brakes, so the acronym means Tons Per Operating Brake.
Each two bogie freight car has a single brake cylinder located near the middle of the freight car that applies the braking force to the brake shoes via beams and levers, so all normal freight cars have one brake system and are counted as one. Articulated Piggyback Flatcars and 5 section Doublestack Well Cars are different. US freight cars carry heavier weights than those in Europe, many freight cars have a loaded weight of 134 tons, but the majority of freight cars built in the last 10 years have a loaded weight of 143 tons. So it will take a fair number of empty freight cars to get the average down.
This is reasonable, we in Europe have similar constraints but expressed in metric tonnes/axle usually (typical situation): - run at 20 tonnes/axle load: 120 km/h (75 mph) - run at 22.5 tonnes/axle load: 100 km/h (62 mph) So, a 4-axle wagon could run on a flat or rising route at up to 62 mph loaded at 90 metric tonnes (= 99 tons) total weight. That is practically equivalent between us, don't you think? The speed limit on down grade does have to do with the combination of grade and kinetic energy, and it must include: track curvature and thermal capacity of air brakes. As per the NTSB report mentioned above, the dynamic braking must not figure in this calculation - the air brakes must be enough for fully stopping the train. Now, what happens when you have empty wagons in your train? Does their braking force enter the calculation? I suspect that the numbers you quoted above are *average* numbers for the whole consist. N.F.
So here is a typical mixed manifest train on the Soo Line with the count and weight as it departed LaCrescent, MN yesterday after making a pickup and setout;
Train 270 (St. Paul to Kansas City)
97 loads
79 emptys
14,587 tons
That yields a TPOB of 84.3, on the BNSF that train would be allowed to run at 60 mph.
The train had 2 SD60s and a SD40-2 for 10,600hp or 0.72hp per ton.
JB
beaulieu So here is a typical mixed manifest train on the Soo Line with the count and weight as it departed LaCrescent, MN yesterday after making a pickup and setout; Train 270 (St. Paul to Kansas City) 97 loads 79 emptys 14,587 tons That yields a TPOB of 84.3, on the BNSF that train would be allowed to run at 60 mph. The train had 2 SD60s and a SD40-2 for 10,600hp or 0.72hp per ton. JB
With that loading - being allowed to run 60 MPH and being able to run 60 MPH with the power listed are two different realities.
Ironeagle2006 Doing my Math and figuring out the Physics in my head that Engineer maybe had a top end of around 45-50 MPH before he flat out ran out of TE on the Engines. Any Curvature or Slight Grade up and he was going to be on his KNEES. But then again when CNW first broke into the Powder River Basin UP would move the 15K ton trains with only one SD60M on the point.
Doing my Math and figuring out the Physics in my head that Engineer maybe had a top end of around 45-50 MPH before he flat out ran out of TE on the Engines. Any Curvature or Slight Grade up and he was going to be on his KNEES. But then again when CNW first broke into the Powder River Basin UP would move the 15K ton trains with only one SD60M on the point.
Very little railroad mileage is truly level - watching the load meter on a tonnage train will tell you where the grades are that your eyes can't see - and there are a lot more of them than you realize.
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